Röntgenstrukturanalysen von Chiralen Ionophoren: NH₄NCS‐Komplex von 9,9′‐Spirobifluoren‐22‐Krone‐5

Abstract

X‐ray Structure Analyses of Chiral Ionophores: The NH 4 NCS Complex of 9,9′‐Spirobifluorene‐22‐crown‐5 In the crystalline NH 4 NCS complex of 9,9′‐spirobifluorene‐22‐crown‐5 ( 1 ) the NH ion sits in the centre of the polyether ring, with distances of 2.92–3.15 Å to the five O‐atoms and shows at least twofold orientational disorder. In one orientation, three H‐atoms point toward O‐atoms and the fourth to the N‐atom of the anion situated 2.78 Å above the polyether ring. In another, only two H‐bonds are formed. The mean planes of the two fluorene parts of the molecule are perpendicular to each other. Crystals of 2,2′‐bis (hydroxymethyl)‐9,9′‐spirobifluorene ( 2 ), an intermediate for the synthesis of 1 , contain occluded benzene, which cannot be removed under vacuum. X‐ray analysis shows that the benzene molecule does not interact with the spirobifluorene in a specific way but merely occupies cages in the crystal packing.